Correct Answer - C
Let both balls meet at point `P` after time `t`.
The distance travelled by ball `A, h_1 = (1)/(2) g t^2`
The distance travelled by ball `B, h_2 = ut- (1)/(2) g t^2`
`h_1 + h_2 = 400 m`
`rArr ut = 400, t = 400//50 = 8 m`
`:. h_1 = 320 m and h_2 = 80 m`.